Glide Distance Calculator

Frequently Asked Questions

How far can I glide from altitude?

Glide distance (NM) ≈ altitude AGL (ft) × glide ratio ÷ 6,076. A C172 at 6,000 ft AGL with 9:1 best-glide ratio: 6,000 × 9 ÷ 6,076 ≈ 8.9 NM in still air.

What glide ratios are typical?

C172: ~9:1. Cirrus SR22: ~9:1. Diamond DA40: ~10:1. Light twins: ~10:1 single-engine clean. Modern sailplanes: 30–60:1. Always fly the POH's best-glide speed, not max-L/D from theory.

How long do I have aloft?

Time (min) = altitude AGL ÷ sink rate (fpm). At best-glide a C172 sinks ~700 fpm, so 6,000 ft AGL gives ~8.6 min of decision time - enough to declare, troubleshoot, brief passengers, and pick the best field.

How does wind change usable glide?

A 20 kt headwind at 65 KIAS halves your ground glide; a tailwind extends it. Always plan emergency landings considering current winds and choose into-wind options when possible. Educational only - verify with POH glide data.

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Aviation & Marine Disclaimer: Educational only. Not for flight or navigation operations.

This calculator is for educational and informational purposes only and is not a substitute for official flight or navigation planning. Always use current performance charts, an approved POH/AFM, certified navigation tools, and follow all applicable FAA, ICAO, USCG, and other regulatory guidance. Verify all results independently before operating any aircraft or vessel.

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How This Calculator Works

When the engine quits, the only resource the pilot has left is altitude - and altitude turns into distance at the rate set by the aircraft's best-glide lift-to-drag ratio (L/D). Knowing how far you can glide from any given altitude is the difference between making a runway and landing in trees: pilots are taught to maintain a continuous awareness of the “footprint” of reachable terrain. This calculator takes altitude above ground level (AGL), the published or estimated glide ratio at best-glide speed, and the sink rate at that speed; outputs the still-air glide distance in nm/sm/km and the time you have aloft. It also discounts the raw figure by about 15% to give a realistic reachable radius once you account for wind, a circle-to-land, and the energy lost in any required turn. Use for planning study; the POH best-glide speed and the actual wind govern the real answer.

Formula / Method

Best-glide distance (ft) = altitude AGL × (L/D). Convert to nautical miles by dividing by 6,076.12, to statute miles by 5,280, to km by multiplying by 0.0003048. Time aloft (min) = altitude AGL ÷ sink rate (fpm). The L/D figure must be the value at the published best-glide indicated airspeed (V_BG or V_L/D) and at the aircraft's gross weight; it changes with weight (V_BG shifts) and with flap/gear position. Real-world distance is reduced by headwind component and by any turn (a 30° bank loses about 10–15% of energy due to higher induced drag).

Worked Example

Engine out at 6,000 ft AGL in a typical light single with L/D ≈ 9:1 at best glide and a 700 fpm sink rate at that speed. Glide distance = 6,000 × 9 = 54,000 ft ≈ 8.88 nm. Time aloft = 6,000 ÷ 700 ≈ 8.6 min - enough to set up a forced landing if a field is within roughly 7–8 nm and the wind is benign. A 20-kt headwind on the glide trims roughly 1.5 nm off the reachable distance (8.6 min × 20 kt ÷ 60 ≈ 2.9 nm into wind). High-performance gliders have L/D ratios of 40–60 and can stay aloft for hours.

Common Mistakes

Using MSL altitude instead of AGL - what matters is height above the terrain you intend to land on. Forgetting that flaps and gear destroy L/D - leave both up until landing is assured. Flying faster than best glide hoping to “cover ground” - you actually cover less; best glide is best for a reason. Trying to stretch a glide by raising the nose - you reduce airspeed below best glide and sink rate jumps. Ignoring wind - into a strong headwind, accept a steeper-than-best-glide approach to retain energy for the round-out.

Tips & FAQ

What is the L/D of a typical light single? Roughly 7–10:1; high-wing trainers around 9:1, slick low-wing singles often 10–12:1. How do I find best-glide speed? The POH lists it as V_BG or as the airspeed at the top of the "Maximum Glide Distance" chart. Should I extend flaps or gear? No - clean configuration gives best L/D; configure only when landing is assured. What about turbulence and gusts? Add 5–10 kt to V_BG for better penetration; sacrifices a little distance but reduces stall risk. Disclaimer: planning study only; the POH/AFM and current conditions govern the real glide.

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